Feed control for liquid refrigerant



Patented Jan. 29, 1946 2,393,854 FEED CONTROL FOR LIQUID REFBIGERANT Thomas E. Carpenter, New York, N. Y.: Elizabeth C. Carpenter admlnistratrlx of said Thomas E.

Carpenter, deceased Application January 31, 1942, Serial no. 429,042

.- '1 Claims. (01. 62-12'l) My invention has reference to the well-known type of refrigeration system wherein a volatile refrigerant is evaporated, compressed and condensed and it relates particularly to the feed control by which the flow of liquid refrigerant to the evaporator of such a system is regulated. In my Patent No. 1,919,500 there. is disclosed an im proved feed device for such systems and my present invention relates to the addition of further steps of improvement to that device. The device covered by the patent comprises a single restrictive tube arranged between connector fittings for inclusion in the liquid supply pipe and for use as a pressure reducer, whereas my present invention comprises a liquid feed unit providing two steps ofpressure reduction, together with an adjustment for the second step and a safety strainer for the liquid stream. I now combine with a restrictive tube forming one step of pressure reduction, a second control step that produces a further pressure reduction, and this second step is also adjustable to different sizesso that differing amounts of pressure reduction may be accomplished by it. I prefer to have this adjustable element made so that it will remain fixed after each adjustment has been made but it may also be made automatic.

The restrictive tube control disclosed in my Patent 1,919,500 is now widely used for household refrigerators and small units of a standardized character, and the advantages of such a feed control where the compressor operates intermittently are well known. It has been found, however, that seasonal changes, and in some locations even daily weather changes, create pressure differences at the condenser that tend to interfere with the uniform operation of such units. Because of the known advantages of the restrictive tube feed control; in connection with mechanisms where intermittent compressor operation takes place, it now seems desirable to utilize such controls on a wider variety of commercial refrigeration apparatus where standardized production is the rule. But such apparatus is frequently subjected to a much greater variation of pressures than the household refrigerator, and it is subject not only to changes in condenser pressures, but it is also used for refrigeration applications requiring low cooling temperature for some purposes and high cooling temperatures for others. Therefore, evaporator pressures will vary considerably on such commercial equipment.

One object of the present invention is to comblue the advantage of the restrictive tube control, "wherein the high and the low pressures its tendencyto overfeed or underfeed at times equalize while the compressor is idle so that it may restart more easily, with means for offsetting when pressures change beyond its narrow limits. Another object is to combine, within the control unit itself, a safety screen for protecting the tube against choking if small particles, of dirt or scale are caught there.

Another object is to provide a feed control that will afford a wide range of adjustment so that it may be manufactured in quantities at lower cost and yet may be adapted to widely different cooling temperatures and pressures.

Another object is to provide an expander device for reducing the pressure of liquid refrigerant in standardized capacities and yet each unit be quickly adaptable to a number of refrigerating loads.

Yet another object is to devise a control of this class that may also combine the functions of an accumulator and heat exchanger for counter current flow of return gas from the evaporator to the compressor in close relation with the outer surface of the restrictive tube.

Referring to the drawing, which is made a part of this application and in which similar reference characters indicate similar parts:

Fig. 1 is a diagrammatic elevation illustrating a method of embodying my invention in a refrigerating system.

Fig. 2. a vertical longitudinal section of a preferred form of my device.

Fig. 3, an elevation of another form, and

Fig. 4, an elevation of still another form of the invention.

, ,In' the drawing reference character lllindicates the motor driven compressor from which the refrigerant passes to condenser II which is connected by a pipe I! to the pressure reducing feed control ll from which the refrigerant passes to evaporator I4 and thence back to the Jacket of the device I! as hereinafter explained, and thence through pipe I! back to the compressor I0.

In that form of the feed control which is shown in Figure 2 there is a restrictive pipe l6 of the type also known as a capillary tube, this pipe being shown as being in the shape of a helix. It will be understood that the pipe l6 may be of any suitable or conventional shape. At opposite ends the pipe I6 is connected to suitable fittings for placing it in circuit with other elements used to form the refrigerating cycle. In the drawing I have shown one of said fittings as having an inlet head I! with a central passage l8 into one end of which an end of tube l6 fits. Theother end of the inlet head is shaped to provide a mantle internally threaded at l9 to receive an end fitting 20 threaded at both ends and having between its threaded ends a radial flange 2| limiting its screw movement into the mantle. The threaded outer end 22 serves to connect the end fitting to pipe H. in any suitable manner and this fitting has an inlet passage at 23 for refrigerant. The portion of the end fitting inside the mantle has secured therein as by means of solder a conical strainer 24, the wall of said strainer being spaced from the interior of the fitting so that the refrigerant may flow from the passage 23 over any part of the strainer and then pass through the same into the hollow interior of the inlet head.

At the other end of the restrictive tube l8 there is an outlet head 25 having a central passage at 26 to receive one end of the tube IS. The central passage leads to an intermediate pressure chamber 2l into which is screwed an outlet fitting 28 forming the outlet from said chamber to the evaporator l4 and provided with a lock nut 29. A valve 30, threaded in the outlet head, has a tapered inner end adapted to be seated in a seat at the inlet end of chamber 21, or to be withdrawn to varying distances from the seat so as to provide a variable inlet capacity for said chamber, i. e., a throat of variable capacity. The valve-is provided with packing at 3| and a gland 32 is threaded into the head, these parts being covered by a cap 33. When the cap is removed the valve can be adjusted, as by means of a screw driver engaging a slot in the end of the valve stem.

In the form of the invention shown in Figs. 1 and 2 there is a casing surrounding the tube l6 and comprising a tubular body 34 of suitable length, the body being closed at its ends by end members 35 and 36 fitting closely about the inlet and outlet heads I! and 25, and connected thereto in any convenient way so as to prevent leakage. The body is provided with an inlet nozzle 31 for return gas from the evaporator, and with an outlet nozzle 38 for connection to pipe l5. These adapted since these refrigerating units had to stop and start frequently, and it is very desirable that the starting load for the motor be made easier. This device permitted liquid to flow after the compressor stopped until the evaporator pressure equalized with the condenser pressure, and then it was only necessary for the motor to overcome the compressor friction and momentum when starting. However, I have found that there can be enough change of condenser pressure un der the temperatures existing at the locations where household refrigerators are frequently placed so as to seriously impair the uniform operation of that first control. And, in addition,

I have found that much advantage may accrue to the user of smaller commercial apparatus, such as ice cream vending cabinets, water coolers, and the like, when there is attached to such apparatus a feed control of the restricted tube type that may bechanged for different pressure combinations and flow quantities on the evaporator side. Therefore, I have developed other devices for use with the restrictive tube so that the liquid flow may be adjusted to suit the required duty when pressure conditions are changed, either because of different condenser pressures or different evaporator temperatures, or both of these. It should be stated here that for the classes of refrigeration applications I have mentioned simplicity of design and adaptability to definitely sure adjustments are great advantages, for frequent service calls are almost prohibitive on acv count of cost alone.

and other connections may be made by means of the well-known pipe clamps or in any other desired manner. ternative outlet nozzle such as may be used if desired. Both nozzles 38 and 39 may be provided and one closed off, or only one may be provided, according to anticipated conditions ofuse, etc.

I do not claim the gas-tight casing or the method of passing cold returned gas through the unit as part of my invention. For the needs of many users I-will employ a perforated casing or skeleton frame of any suitable type as a support to which the end fittings l1 and 25, with their assemblies, will be attached. In such cases the gas return fittings 31, 38, 39 will be omitted.

My original conception of a pressure reducing device (asshown'in Patent No. 1,919,500) had for its main object its use with the smaller fractional ton refrigeration units such as the household refrigerator. For such a purpose it was well At 39 I have indicated an alsure occurs, whether it be in the condenser or- It is also well known that a control device of the restrictive tube type may be installed where there is no liquid strainer to catch dirt and scale. I construct these devices so that a strainer is contained within the unit and therefore always protecting the tube inlet.

In the use of the device above described the refrigerant .fiows from the condenser through pipe l2 to the pressure reducer and thence to the evaporator, the screen preventing any scales or particles of dirt from entering and clogging the restrictive pipe [8. This pipe, as in the case of my prior patent, furnishes a fixed step of pressure reduction determined by the length and diameter of the tube, the results remaining uniform (so far as this fixed step is concerned) so long as the pressure conditions and the quantity required remain the same. At the other end of the tube I provide an adjustable step of presthe valve and the seat and so may provide a further reduction in the pressure of the refrigerant before it reaches the evaporator.

' In a device of this style almost any amount of adjustment can be secured and therefore wide variation of pressures may be controlled so as to secure substantially uniform operation of the refrigerating system. When a change of presthe evaporator the cap 33 may be removed and valve 30 adjusted in either direction to compensate for such different pressures. The packed V stem permits this adjustment to be made at any time and as often as desired. 7

I should also direct attention to the fact that this device permits adjustment of the second step in a direction parallel to the change in the first step as well as in a direction opposed thereto, i. e., when the pressure change creates an in-' creased flow through tubelli as the first step, the second step may be adjusted to pass an increased quantity rather than to compensate and reduce the increased flow past the first step. A refrigerating system that is applied to a new" duty where the ratio of pressures is greater and the duty to be performed is also greater would be an example of such a case.

The return fiow of refrigerant from the'evapo rator flows through the Jacket formed by'tube l3, combining the functions of an-accumulator and a heat exchanger for countercurrent flow of the return gas from the evaporator to the compressor in close relation to the restrictive tube. This space is also adapted for suction accumulator purposes, 1. e., for catching any entrained liquid that gets by the evaporator when the compressor starts or at other times. In some of the lower temperature applications this function is important. In such cases the device of Fig. 2 will act not only as the feed control or expander, but also as a heat exchanger and an accumulator. By such combination the construction costs to be borne by the owner or ultimate user are very much reduced, for three purposes are satisfied with the one device.

In the device of Fig. 3, the parts numbered similarly to those inFig. 2 are or may be identical with like parts in Fig. 2. The head 40 has a flange 4! that rests against theend inember 85 and is threaded to receive a fitting 42 which clamps the flared end of outlet tube 43 between a conical face on said fitting and the conical face of outlet fitting 44 which is clamped between said fiared pipe portion and the adjacent end of the head 40. The outlet has a throat 45-, and this provides a second reducing step for the re-.

frigerant in the intermediate pressure chamber between the fitting 42 and the adjacent end of the restrictive tube, which step is made variable i. e., is adjustable to varying pressure ratios, in that the fitting 42 may be unscrewed and an outlet fitting having an orifice of different size may be substituted for that one which is in use. When designing such a two step feed and pressure reducing unit I select the length and size of the tube and also the throat which constitutes the second step so as to have a combined pressure reducing means suitable for the unit to be supplied.

Thus I am able to adjust the second step within reasonable limits, in either direction, to make the design suit other pressure combinations when they occur. Then if the refrigerating machine to which the unit is'attaohed is to be applied to a different cooling temperature, the resulting pressure change may be met and the operation still be substantially uniform.

' The substitution of outlet fittings as shown by Fig. 3 is suited to refrigerating units that do not often experience pressure changes wide enough to require a substitution of throats. temperature effect on the condenser pressure is an example of this kind. For such infrequent and narrow changes the substitution of throat fittings is a desirable'method of providing the compensation needed because it also insures that no one but the proper party can tamper with this element. In this form of the invention, as in that shown in Fig. 2, the second step of adjustment may be in the same direction, so as to re- Seasonal is provided for connection to an outlet pipe, the

head having a flange 41 bearing against the end member 85. Here, as alsoin Fig. 3, one end of pipe I6 may be left disconnected from its head,

that various changes and modifications may be made in the device, all without departing from the spirit of the invention, and therefore I do not limit, myself to what is shown in the drawing and described in the specification, but only as indicated in the appended claims.

Having thus fully described my said invention,

what I claim as new and desire to secure by Letters Patent is:

1. A refrigerant expander comprising an outer casing, a capillary tube therein, means carried by the casing for supporting the inlet end of the said capillary tube and conducting refrigerant to said tube, and a device for supporting the outlet end of the said tube and conducting the refrigerant therefrom, said device including manually operable means for adjustably throttling the outlet end of said capillary tube for securing and maintaining desired pressure reduction in the refrigerant discharged from said expander with respect to the pressure of the refrigerant entering the expander.

2. A refrigerant expander comprising a capillary tube, supporting means for the. capillary tube including a device for supporting the inlet end of the capillary tube and conducting refrigerant to the tube, said supporting means also including a device for supporting the outlet end of the capillary tube and conducting the refrigerant therefrom, and a manually operable member cooperating with said outlet and supporting device, said manually operable member being adjustable for securing and maintaining a desired pressure reduction in the refrigerant discharged from the expander with respect to the pressure of the refrigerant entering said expander.

3. A refrigerant expander comprising a capillary tube, a head for supporting the inlet end of said capillary tube and conducting refrigerant to said tubaa head for supporting the outlet end of said tube and conducting refrigerant therefrom, supporting means connecting said heads, and manually operable means for adjustably throttling the passage in the second mentioned head for securing and maintaining desired pressure reduction in the refrigerant discharged from said expander with respect to the pressure of the refrigerant entering said ex- I pander.

duce the pressure further, or it may be in the 4. A refrigerant expander having a head with an inlet passage, a head with an outlet passage, supporting means connecting said heads, a capillary tube carried by said heads and serving to frigerant discharged from said expander with respect to the pressure of the refrigerant entering said expander.

5. A refrigerant expander comprising a capillary tube, a head at one end of the tube, said head being provided with an inlet passage for conducting refrigerant to said tube, a head at the other end of said tube, said second men-' tioned head being provided with an outlet passage for refrigerant from said tube, supporting means connecting said heads, and a manually adjustable valve in series with said capillary tube for securing and maintaining desired pressure reduction in the refrigerant discharged from saidexpander with respect to the pressure of the refrigerant entering said expander.

6. A refrigerant expander comprising supporting means, a capillary tube thereon, a device carried by the supporting means for supporting the inlet end of the tube and conducting refrigerant to said tube, and a device carried by said supporting means for supporting the outlet end of the tube and conducting refrigerant therefrom,

said second-mentioned device including a non- 20 temperature responsive valve having an element progressively adjustable for maintaining desired pressure reduction in the refrigerant discharged from said expander with respect to the pressure of the refrigerant entering said expander.

7. A refrigerant expander comprising a pair of heads, .one head having an inlet passage and the other an outlet passage, supporting means for maintaining said heads in fixed relation, a capillary tube positioned to receive refrigerant from said inlet passage and conduct it to said outlet passage, a non-temperature responsive valve in series with said tube to permit a continuous flow of refrigerant, and means for adjusting said valve incrementally to provide desired pressure reduction in the refrigerant discharged from the expander with respect to the pressure of the refrigerant entering said expander.

THOMAS E. CARPENTER. 

